1. Field of the Invention
The invention relates to a process for manufacturing needled spunbondeds wherein, prior to the needling, the continuous filament web is thermally sealed only at the surface with a lubricant.
2. Description of the Related Art
As already known from DE Patent 3,009,116, to obtain advantageous web properties, in particular to obtain a high web strength and web uniformity, it is essential that the web be treated with a fiber finish prior to the needling. The treatment of the webs with a fiber finish prior to the needling improves the sliding properties, which makes it possible to avoid needle breakages during the needling on the one hand and filament damage on the other. The fiber finish in question was applied by means of nozzles or by dipping. However, application by means of nozzles was found to have the disadvantage that the jet action partially destroys the coherence and integrity of the still loose and unconsolidated web. Similarly, dipping of the loose filament assembly, for example in a liquid lubricant bath or in foam, was found to destroy the web structure. It was therefore necessary, before any fiber finish was to be applied, to stabilize the web slightly by means of light preneedling. However, this had the disadvantage that, to avoid excessive damage to the non-fiber-finished web and to avoid needle breakages, the production speed had to be greatly reduced.
According to DE Patent 3,009,116, this disadvantageous operation of preneedling can be eliminated by depositing the still unconsolidated, as-spun web on a rotating sieve drum where the fiber finish in the form of a mist is sucked through the web by means of a vacuum and aspirated away on the inside of the sieve drum via a plurality of suction zones. The disadvantage of this improvement is in particular that the basis weight uniformity of the web is still not satisfactory, that high production speeds are not possible, and that a relatively complicated web formation apparatus involving a vacuu and complicated controls is required.